Performance of Automated Chemiluminescence Assay for Antiphospholipid Antibody Testing

ABSTRACT

BACKGROUND: Detection of antiphospholipid antibodies (aPL) can be considered problematic due to assay variability and reagent sensitivity, high false-positive and false-negative rates, and lack of assay standardization. Therefore, utilizing an automated system can improve reproducibility and reduce interlaboratory variation. Here, we evaluated the analytical performance of the new automated ACL AcuStar chemiluminescence assay (Instrumentation Laboratory, USA). This was compared to the results of a panel analyzed with the QUANTA Lite ELISA (INOVA Diagnostics Inc., USA). METHODS: We evaluated the inter-assay precision, linearity, and carry-over between the two methods, ACL and ELISA. A reference range study for each of the anticardiolipin (aCL) and anti-beta2 glycoprotein-I (abeta2GPI) IgG and IgM antibodies were performed using 135 healthy patient samples, which served as controls. We then compared the accuracy among the AcuStar and ELISA systems via four aPL tests. For this comparison, 69 patient samples suspected of an autoimmune disorder were used as the experimental panel. RESULTS: The AcuStar analyzer showed excellent precision, linearity, and carry-over for all four assays. The calculated cutoff values were 20.3 U/mL for aCL IgG, 20.3 U/mL for aCL IgM, 26.3 U/mL for abeta2GPI IgG, and 11.9 U/mL for abeta2GPI IgM. The consensus between AcuStar and ELISA results were generally comparable. Total agreement varied between 82.6% and 95.7%, and kappa values showed moderate to good agreement. CONCLUSIONS: Our study demonstrates that the new AcuStar chemiluminescence assay showed better performance. This automated system leads to improved reproducibility and reduces interlaboratory variability.